Limit switch operating mechanism



March 26, 1957 R. B. IMMEL' ETAL 2,786,352

LIMIT SWITCH OPERATING MECHANISM Filed Nov. 7. 1951 2 Shee'ts-Sheet 1IRS Fig.6.

WITNESSES: INVENTORS Ralph B. lmmel WK/ BY Martin Wibell 244 7% v MZTWATTORNEY March 26, 1957' R. B. IMMEL ETAL LIMIT SWITCH OPERATINGMECHANISM Filed Nov. 7-, 1951 2 sheetsvsheet 2 Ca-VIQII.

' Fig.5.

INVENTORS Ralph Bxlmmel Martin Wibell ATTORNEY WITNESSES! United tatesPatent LIMIT SWITCH OPERATING MECHANISM Ralph B. Immel and MartinWibell, Williamsville, N. Y., RSSifilOl'S to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of PennsylvaniaApplication November 7, 1951, Serial No. 255,253

1 Claim. (Cl. 74-110) Our invention relates to switches and moreparticularly to switch operating mechanisms as applied to limit switchesand similar other switch uses.

, It is an object of the invention to provide the trade with a reliableand dependable switch operating mechanism.

A more specific object of our invention is to provide an improvedoperating mechanism for a plunger actuated switch which is reliable,durable, and less expensive than prior art operating mechanisms.

A further object of our invention is the provision of an operatingmechanism, for a plunger actuated switch, for translating therectilinear motion of an operating rod actuated by some machine, such asa milling machine, into rectilinear motion perpendicular to the line ofaction of the operating rod.

It is an additional object of our invention to provide an operatingmechanism, for a plunger actuated switch, for translating therectilinear motion of an operating rod into rectilinear motionperpendicular to the line of action of the operating rod to actuate theplunger operated switch.

Another object of our invention is the provision of operatingmechanisms, for a plunger actuated switch, for translating therectilinear motion of an operating rod into rectilinear motionperpendicular to the line of action of the operating rod to actuate theplunger operated switch without producing a wiping or sliding motionbetween the operating mechanism and the switch plunger.

The aforesaid objects of our invention, and other objects of ourinvention not expressly recited, are achieved by providing an elongatedleaf spring disposed in a slightly flexed position between two movablesupports, the supports being movable linearly by equal amounts towardthe middle of the spring in response to movement of the operating rod tocause the middle of the spring to move in a straight line normal to theplane of the spring to thus actuate some mechanism such as a switch.

For a better understanding of the invention reference should be made tothe accompanying drawings, wherein:

Figure l is a vertical sectional view through the housing showing a sideof one embodiment of the invention, the section being substantially onthe line I-I of Fig. 2, looking in the direction indicated by the arrowsat the ends of the section line;

Fig. 2 is a sectional view along line II-II of Fig. 1 looking in thedirection indicated;

Fig. 3 is a front view of the device with a part of the front coverbroken out and certain elements omitted;

Figs. 4 and 5 show front and side views of the operating cam; and

Fig. 6 shows a view of the operating rod.

It will be apparent from the showing in Fig. 1 that the housing 1 whichencloses the operating components of the device consists of a front orcover 2 and a rear portion 3. The rear portion 3 houses a plungeractuated type switch 4. The plunger 5 of the switch projects from theswitch casing and actuates the switch with a snap 2 action when theplunger 5 is moved axially a selected distance.

The switch 4 is rigidly secured to the cover 2 of the housing 1 by bolts6 and 7 and the rear portion 3 of the housing 1 is rigidly secured tothe cover 2 by bolts 8 and 9.

The operating components include bearing bushings 10 and 11, which actas guides and bearings for the oper-v ating rod 12, rigidly secured tothe die cast cover2, as may best be seen in Fig. 3.

The operating rod 12 is provided with an enlargemen 13 which acts as athrust bearing against the upper bushing 10 to limit the upward movementof the operating rod 12. The lower end portion 14 of the operation 'rod12 is of a smaller size than the rest of the rod to provide a bearingsurface 15 for the cam 16. A helical spring 17 surrounds the lower partof the reduced portion 14 of the operating rod 12 and rests on the lowerbushing 11, the other end of the spring 17 supports the cam 16 andserves to bias the cam 16 into position against its bearing sur-. face15 on the operating rod 12, to thus bias the enlarge ment 13 on theoperating rod 12against the upper bushing 10.

The cam 16 is so positioned on the operating rod 12 that its surfacesare disposed between the rollers 31 and 32 on the bell crank levers 27and 28. The bell-crank levers 27 and 28, identical in design, areprovided on bearing pins 29 and 30, which are cast into the cover 2 andthe horizontal arms of the bell-crank levers are provided with springsupport elements 33 and 34 respectively. The spring support elements 33and 34 are rollers with fiat bottomed hardened V-shaped bearingsurfaces, adapted to receive the ends of the leaf spring 35. The leafspring 35 being so dimensioned that it is normally disposed or clipped,in an arcuate position between the rollers 33 and 34. The pivots 29 and30 are provided for the bell-crank levers 27 and 28 in order that thespreading of the rollers 31 and 32 on the vertical arms of thebell-crank levers, upon a vertically downward movement of the cam 16 bythe operating rod 12, will rotate the bell-crank levers clockwise andcause the spring support elements 33 and 34 to move equal distancestoward each other, thus moving the middle of the spring 35 in thedirection of the plunger 5 and in the line of movement of the plungerfor actuating the switch 4. The leaf spring 35 biases the bell-cranklevers for counterclockwise movement to assure firm contact between theends of spring 35 and spring support elements 33 and 34 on thehorizontal arms of the bell-crank levers and between the cam contactingrollers 31 and 32 on the vertical arms of the bell-crank levers and thesurfaces of cam 16.

When operating rod 12 is depressed, cam 16 is also moved in the samedirection and the helical spring 17 is compressed. The movement of cam16 in a downward direction causes the rollers 31 and 32 on the verticallegs of bell-crank levers 27 and 28 to ride up on the wide portion ofthe surfaces of the cam 16. Thus, the bellcrank levers 27 and 28 arerotated clockwise through equal angles.

The clockwise movement of bell-crank levers 27 and 28 through equalangles causes spring support elements 33 and 34 to move equal distancestoward the axis of the plunger 5. This causes the middle of the lea-fspring 35 to move in a straight line perpendicular to the line ofmovement of the operating rod 12; the line of movement of the leafspring 35 being along the axis of the plunger 5 to actuate the snapswitch 4.

The apparatus described and shown, in addition to providing a simplemeans for operating the switch 4 has other noteworthy features. Themechanism provides considerable movement amplification through leafspring 35. A slight decrease in distance between the spring supportelements 33 and 34 results in a relatively large deflection of themiddle of .leaf spring 35 perpendicular to its axis. With hardened Vshaped bearing surfaces in spring suppQrte'Iements-SS'and -34, a leafspring of proper selection, and the provision of hardened rollers andcams, the mechanism will operate for "millions of operations withoutwear and without any 'change in the operating point.

The surfaces of the cam 16 above the rollers 3-1 and 52 are'parallel tothe direction of movement of the cam and the operating rod 12 so thatthe spring support elements'33-and '34Will be moved only a fixeddistance toward each other regardless of the distance of travel oftheoperatingrod 12.

"The helical spring 1'2, which is subjected to compression when theoperating rod '12 is-depressed, returns the parts to their neutralposition as soon as the operating rod is released by the actuating dogon the machine.

While but a single embodiment of the invention has been shown anddescribed, it will -he apparent to those We claim as our invention:

Iii-operating mechanisms for a plunger actuated device, comprising incombination, a base, a bell-crank lever pivotally mounted on the base,spring support means on one arm of the bell-crank lever, a correspondingspring support means disposed on the base in spaced relation to thespring support means on the hell-crank lever, a flat spring arcuatelyclipped between the spring support means, spring retaining means at theengagement of the spring ends with the spring support means, said springretaining means and end pressure on the spring constituting the solesupport for said spring, a cam disposed adja' cent the other leg of thebell-crank lever, and means for T imparting a rectilinear motion to thecam to rotate the hell-crank lever through a. selected angle to thuseffect a selected movement of the spring support means toward each otherto thus make the spring are more convex to actuate the plunger.

References Cited in the file of this patent UNITED STATES PATENTS"FOREIGN PATENTS France June 27, 1927

